Why doesn’t Wellington have enough water storage for a dry summer?

Saturday, 3 February 2024

The Te Mārua lakes hold about 45 days worth of water. In summer the lakes are crucial to keeping our taps flowing when other sources like the Hutt River dry up.

There has been a lot of focus on leaks and their contribution to the current water crisis but as Nicholas Boyack points out, it is easy to overlook the elephant in the room, the lack of storage facilities.

Any way you dress it up, the region’s lack of water storage is a débâcle.

Wellington’s water comes from a number of sources but in summer, we become heavily reliant on two storage lakes in Upper Hutt, which hold 3.35 billion litres of untreated water. As the other sources dry up and Wellingtonians use more water, the Te Mārua lakes become critical to keeping our taps flowing.

Wellington Water chief executive Tonia Haskell says the lakes have enough storage for about 45 days. The lakes supplement the aquifer and as long demand is steady, they can be relied on for seven weeks. She notes, however, that relying on the lakes is a “high risk” strategy.

An aerial view, looking south towards Upper Hutt, showing the Te Mārua Lakes under construction in May 1984.

Local authorities have known since the 1990s that with so little storage and a growing population, that we could one day run out of water. The situation has only become worse in recent years due to the leaky pipe network.

A Greater Wellington report dated September 2005 noted the region’s population was growing and a “major new water source” was needed by 2011. The only action recommended by the Utilities Committee was to issue a press release.

Council reports and Stuff stories from the early 2000s until about 2013 all have the same theme - we probably need to build a dam but we can avoid the expenditure of doing so by saving water. Rather than invest in much needed infrastructure, politicians lobbied for such water saving measures as encouraging garden mulching and showering with a friend.

A number of sites for dams were explored, with the preferred options all in Upper Hutt. By 2008, it was agreed that the best option was a dam on the Whakatikei River, costing $142 million.

Players and staff from the Hurricanes help with the mulch at a Stokes Valley community garden. Mulching has been suggested as an alternative to building new dams. (File Pic)

When it came to getting political support, however, the project died a quiet death and 14 years later, we are on the verge of running out of water.

John Morrison, who worked for Wellington Regional Water Board and then the Wellington Regional Council from 1975 to 2008, says Whakatikei was a major opportunity lost.

Te Awe Kairangi/Hutt River from Silverstream bridge looking north towards Upper Hutt. In summer, the amount of water in the river falls and the region becomes more reliant on the Te Mārua lakes.

Although much of the current focus is now on how to supply the region with water in a dry summer, he says the work done on Whakatikei looked at a much bigger issue - how to make sure the capital city still has drinking water after the big shake. That issue, he says, remains unresolved.

When the Whakatikei project was proposed and investigated, it had two goals. One was to increase storage and provide for growth across the region, and to provide an alternative source to supply the northern areas of Wellington from Porirua to Karori, including Tawa and Johnsonville.

Morrison notes that the Whakatikei dam was investigated to the point where Ernst and Young produced an economic analysis which came out in favourably of a dam.

The case for a dam was “compelling” but with a hefty price tag it was abandoned.

“Councillors of course took the easy way out so the scheme was dropped,” he said.

Reports from that time present a rosy picture of the water supply network. Personal water use was declining across the region - except in Porirua, where it was going up, although no one knew why - and council papers barely mention the word leak.

Wellington City was spending $108,000 a year fixing leaks and an October 2009 Greater Wellington report noted Wellington City councillors had agreed to use “water conservation” methods to hold Wellington’s water use to 2009 levels, until 2025.

Wellington Water boss Tonia Haskell says relying on two storage lakes in a dry summer is a risky strategy.

In what can only be described as wishful thinking of the highest order, the water conservation techniques listed included mulching gardens, newspaper advertising to encourage people to use less water and an insert in the New Zealand Gardener.

A Wellington City report that same month to the council strategy and policy committee outlined the efforts to avoid increasing water storage nicely. It claimed that Wellington had no water issues.

“Wellington has been fortunate in that it has had plentiful and relatively cheap water in the past and this has masked the need to manage our demand for water.“

This report focused on using “demand management” to defer the need for new storage facilities.

“At its meeting on 12 June 2008 the committee instructed officers to investigate and develop a water demand management strategy. Further to this, the committee resolved on 11 September 2008 that all efforts to manage/reduce water consumption be considered to delay or avoid the need for and the cost of a new dam and that officers continue to work with Greater Wellington Regional Council to that end.”

Wellington’s water comes from a number of sources but in summer, we become heavily reliant on two storage lakes in Upper Hutt.

Despite noting that in a dry summer the Te Marua Lakes only had enough water for 20 days, the report was heavily in favour of encouraging people to use less water to avoid the cost of a new dam, $142m.

“In pursuance of the vision of a sustainable water future for Wellington it is proposed that no major new infrastructure be constructed until all practical and economic conservation and efficiency measures have been pursued, effectively deferring the need for a dam until we have exhausted water savings opportunities. To do this we will need to commit to finding the water we need to cater for growth through savings generated by conservation and efficiency initiatives.”

The report went on to recommend a “water neutral” position that would require per capita consumption to drop at a rate that corresponded with population growth.

Water for the aquifer that provides Wellington with much of its drinking water is fed from Te Awe Kairangi/Hutt River.

“This is aimed at deferring a dam, and progressing towards a sustainable water future through more efficient use of water.”

The strategy required a 15% reduction in water use from 415 litres per day to 350 per day by 2025.

Like all the reports from that time, there was no mention of leaks or the ageing network.

The last significant mention of the Whakatikei dam in the Dominion Post was in April 2013. It had been a particularly dry summer and Wellington had been close to running out of water.

Residents were asked to conserve water by showering with a friend. The council was looking at two options to increase storage, including Whakatikei which by then had risen to $160m.

“Councillor Paul Bruce said getting people to routinely conserve water was a better solution than spending millions of dollars on additional water storage.”

Council chair Fran Wilde said the drought had provided a great opportunity to change people's attitudes for good.

'We will be talking to Wellingtonians about the facts of life and how much they can save off their rates if they just conserve [water].'

Fast forward 11 years and the region is still years away from increasing its storage capacity. Greater Wellington, which is responsible for bulk water supply, is standing firm on its stance that new storage facilities cannot be justified until the four councils - Wellington, Porirua and Upper and Lower Hutt - support water meters.

Now, instead of promoting mulching and showering with a friend, Wellington Water is struggling to fix more than 3200 leaks and is encouraging people to have two minute showers.